Hello,
Well let me start off with this. No matter who says what, if it's Tim Nias, Matt Bonnet, Dave Barker or the queen of England... you don't really know what it is and can't sell the offspring as anything more than Carpet X's of some sort, believed to be " blah blah blah".
That said, you can start crossing things off of the list such as:
Pure Jungle Carpet
Pure Irian Jaya Carpet
Pure Diamond Python
I must admit that cryptic pattern is a bit unique and unlike any carpet i've seen personally. Although this doesn't mean much, who am I? If I was to guess though, could be a 2 or three way cross. Coastal, Diamond or Coastal, Jungle Diamond.
There is an area in Australia where Coastals integrade with Diamonds (Not Jungles with Diamonds, as some say...)
As far as it being a Metcalfei ... I would doubt that quite sincerely. Simply from the financial aspect. Such an animal would rarely be hybridized, would rarely enter into the pet trade and rarely end up in an unknowing persons hands only to be sold in the local classifieds... Granted stranger things have happened, but I doubt most of those things too!
My advice, find yourself a nice funky looking Coastal X Jungle or Coastal X Diamond to breed to it... and Sell the babies as Carpet X's.... That way you don't cross it into anything already "pure"... since you previously stated you don't like hybrids.. this is the most puritan way to go about it, versus keeping it solely as a pet.
hasta,
J